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[DPRG] stella driving down a path

Subject: [DPRG] stella driving down a path
From: Chris Jang cjang at ix.netcom.com
Date: Sat May 12 08:39:49 CDT 2007

Thanks - my mom asked me why Stella drove off the path. It is
a good question and deserving of an answer. I think the answer
is interesting as it is visually obvious.

http://golem5.org/video/mvi4027_crash.jpg

Improvements to any one of the following will prevent this failure.

1. more reliable and higher framerate camera system
2. more sophisticated computer vision algorithms
3. a real control system with a model of the environment

Number 1 is constrained by the hardware. That is for the next robot.

Number 2 is applying what I already know. Like Stanford's robot, I
think Stella will have to use statistical methods. Even with a
multi-million dollar robot like Stanley, there was a point beyond
which improving the hardware to eliminate noise was too expensive.
So it had to be done in software.

Number 3 is stuff I need to learn. Stella needs to have an adaptive
control strategy. This also implies a re-architecture of the
software into a modular form. At this point, I may move the higher
level code into C++. However, the low-level code will remain in C.
And the user interface code for the LCD, pushbutton and radio is in
the Lua scripting language. I am trying to use the optimal level of
abstraction for different problems.


-----Original Message-----
>From: Charles Thurston <cthurston at sc.rr.com>
>Sent: May 12, 2007 7:47 AM
>To: dprglist at dprg.org
>Subject: Re: [DPRG] stella driving down a path
>
>Hello Chris,
>
>Impressive
>
>Friday, May 11, 2007, 9:35:17 PM, you wrote:
>
>> http://golem5.org/video/mvi4027.mpg
>
>> Hello Everyone,
>
>> Here is Stella again. There are no changes to the simple
>> obstacle avoidance algorithm from the last movie in a
>> parking lot. What's going on is purely reactive behavior.
>> There is no path planning or kinematic model.
>
>> Note that Stella has no sensors other than a USB webcam
>> running at around 1.3 frames per second.
>
>> It looks interesting but really there is a lot of work to
>> do. The computer vision is the simplest possible - look
>> for a clear patch of ground immediately ahead - and
>> ignores a lot that is useful. There is also no control
>> model. I just picked constant thresholds and duty cycles
>> for sensing obstacles and driving the motors. It is
>> entirely ad hoc and does not adapt at all. That's why
>> Stella over-corrects. A real control system is necessary.
>
>> By the end of the year, it will probably be necessary to
>> move on to another robot. That will probably be a hobby-
>> grade RC vehicle with at least 10x the computer power.
>
>> Chris
>> _______________________________________________
>> DPRGlist mailing list
>> DPRGlist at dprg.org
>> http://list.dprg.org/mailman/listinfo/dprglist
>
>
>-- 
>Best regards,
> Charles                            mailto:cthurston at sc.rr.com
>
>
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